Pharmacotherapeutic group: Antimycotics for systemic use, other antimycotics for systemic use, ATC code: J02AX08
Mechanism of action
Rezafungin selectively inhibits fungal 1,3‑β‑D‑glucan synthase. This results in inhibition of the formation of 1,3‑β‑D‑glucan, an essential component of the fungal cell wall which is not present in mammalian cells. Inhibition of 1,3‑β‑D‑glucan synthesis results in rapid and concentration‑dependent fungicidal activity in Candida species (spp.).
Activity in vitro
Rezafungin MIC90 values (obtained using a modified EUCAST methodology) are generally ≤ 0.016 mg/L across non‑parapsilosis Candida spp. (Candida parapsilosis MIC90 = 2 mg/L).
When tested against a collection of clinical isolates of Candida spp. enriched for echinocandin‑resistant and/or azole‑resistant strains, rezafungin activity was similar to that of anidulafungin.
Resistance
Reduced susceptibility to echinocandins, including rezafungin, arises from mutations in glucan synthase catalytic subunit‑encoding FKS genes (FKS1 for most Candida spp.; FKS1 and FKS2 for C. glabrata).
Susceptibility testing interpretative criteria
MIC (minimum inhibitory concentration) interpretative criteria for susceptibility testing have been established by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for rezafungin and are listed here:https://www.ema.europa.eu/documents/other/minimum-inhibitory-concentration-mic-breakpoints_en.xlsx
A modified EUCAST broth microdilution MIC methodology has been used for testing the susceptibility of Candida spp. to rezafungin as well as to obtain the respective interpretative breakpoints.
Clinical efficacy
Candidaemia and invasive candidiasis in adult patients
The efficacy of rezafungin in the treatment of patients with candidaemia and/or invasive candidiasis (C/IC) was evaluated in a single Phase 3 study.
The Phase 3 study was multicentre, prospective, randomised and double‑blind. Patients with septic arthritis in a prosthetic joint, osteomyelitis, endocarditis or myocarditis, meningitis, endophthalmitis, chorioretinitis or any central nervous system infection, chronic disseminated candidiasis and urinary tract candidiasis secondary to obstruction or surgical instrumentation were excluded from the study. Subjects were randomised in a 1:1 ratio to receive rezafungin as a 400 mg loading dose on Day 1, followed by 200 mg on Day 8 and once weekly thereafter, for a total of 2 to 4 weeks or caspofungin as a single 70 mg intravenous loading dose on Day 1 followed by caspofungin 50 mg intravenous once daily for a total treatment of 14 days to 28 days.
For rezafungin and caspofungin treatment groups, 77.0 % and 74.2 % patients, respectively, had a final diagnosis of candidaemia only. Most of them had a modified APACHE II score < 20, representing 84.4 % and 81.5 % of rezafungin and caspofungin subjects, respectively. For rezafungin and caspofungin treatment groups, 88.5 % and 91.1 % patients, respectively, had an ANC ≥ 500/mm3 at baseline.
The primary efficacy outcome was global response (confirmed by the Data Review Committee [DRC]) at Day 14. Global response was determined from clinical response, mycological response, and radiologic response (for qualifying subjects with IC). Non‑inferiority was to be concluded if the lower bound of the 95 % confidence interval (CI) for the difference in Day 14 cure rates (rezafungin - caspofungin) was > -20 %. Secondary efficacy outcomes included all‑cause mortality at Day 30 [30‑day ACM] and global response at Day 5. The results of these endpoints are shown in Table 2 for the mITT analysis set, defined as all subjects with a documented Candida infection based on Central Laboratory evaluation of a blood culture or a culture from a normally sterile site obtained ≤ 4 days (96 hours) before randomisation and who received ≥ 1 dose of investigational medicinal product.
Table 2. Summary of results from the phase 3 ReSTORE study (mITT analysis set)
| | Rezafungin (R) (N = 115) n (%) | Caspofungin (C) (N = 117) n (%) | Difference (R-C) (95% CI) |
| Global Response (Cure) [1] | | | |
| Day 5 | 60 (52.2) | 57 (48.7) | 3.5 (-9.4, 16.2) |
| Day 14 | 65 (56.5) | 67 (57.3) | -1.0 (-13.5, 11.6) |
| Day 30 ACM (Deceased) [2, 3] | 29 (25.2) | 29 (24.8) | 0.4 (-10.8, 11.6) |
| [1] Two‑sided 95 % confidence intervals (CIs) for the observed differences in cure rates (rezafungin minus caspofungin) is calculated using the unadjusted methodology of Miettinen and Nurminen except for global cure at day 14 which is calculated adjusting for the two randomisation strata (diagnosis [candidaemia only; invasive candidiasis] and APACHE II score/ANC [APACHE II score ≥ 20 OR ANC < 500 cells/mm3; APACHE II score < 20 AND ANC ≥ 500 cells/mm3] at screening) using methodology of Miettinen and Nurminen. Cochran‑Mantel‑Haenszel weights are used for the stratum weights. [2] Two‑sided 95 % confidence interval (CI) for the observed difference in death rates, rezafungin minus caspofungin treatment group, is calculated using the unadjusted methodology of Miettinen and Nurminen. [3] Subjects who died on or before Day 30, or with unknown survival status. |
Paediatric population
The European Medicines Agency has deferred the obligation to submit the results of studies with REZZAYO in one or more subsets of the paediatric population in treatment of invasive candidiasis (see section 4.2 for information on paediatric use).